Organic polymer coatings, such as acrylics and urethanes, can efficiently block ultraviolet (“UV”) radiation. However, organic polymer coatings can be soft and scratch easily, when compared to an uncoated glass surface. On the other hand, inorganic materials, such as vacuum deposited ceramic oxide optical coatings, can be hard and scratch resistant. Inorganic materials, however, do not efficiently block UV radiation and can result in an undesirable yellow appearance in various applications, including when used to glaze artwork.
Various methods can be used for making coatings for glass that protect against UV light. See, for example, U.S. Pat. Nos. 4,495,360 and 4,122,233, which are incorporated by reference herein. The UV coatings can include a UV absorber that has compounds to absorb radiation of wavelengths starting in the near visible portion of the electromagnetic spectrum, which has a wavelength of around 400 nanometers, to the so-called vacuum ultraviolet portion of the spectrum, which can travel through a vacuum but is blocked by air and has a wavelength of around 200 nanometers in wavelength. These UV compounds can be used to protect items underlying transparent, semitransparent, and/or translucent substrates from the degradative effects of ultraviolet radiation absorption.
Various methods can be used for making abrasion-resistant coatings. See, for example, U.S. Pat. Nos. 6,649,212 and 6,001,163, which are incorporated by reference herein. Hybrid sol gel or Ormosil coatings have been developed to combine features of both the organic polymer coatings and the inorganic coatings. Such hybrid sol-gel coatings can have better scratch resistance than organic polymer coatings and more effectively block UV light when compared to inorganic coatings. U.S. Pat. No. 5,371,138 discloses a hybrid sol-gel UV blocking coating, and is incorporated by reference herein in its entirety. This patent also discloses the uses of methyltrimethoxysilane (MTMS) as an inorganic binder and glycols as a stabilizer in uncured resin. Applications for the hybrid sol-gel coatings include, but are not limited to, glass panes in paintings, art prints, and the like. Currently, for art display applications, hybrid sol-gel coatings based upon a formulation of MTMS binder using glycols are not sufficiently scratch resistant and require careful and experienced handling, especially when cutting the coating glass with a hand or wall cutter, and during assembly of an art picture frame. Therefore, further development is needed to improve the scratch and abrasion resistance for the UV blocking glass coatings so that custom picture framers and art glass fabricators can more easily handle the coated glass products.